Why Oxygen Is 'Expelled' By Comets

One Caltech chemical engineer who tried innovative techniques to create microprocessors in computers has shown why comets expel oxygen. This is the gas that is vital for humans to sustain life.

Researchers exploring the comet 67P/Churyumov-Gerasimenko with the European Space Agency's Rosetta spacecraft made the announcement in 2015. They found that comets release oxygen or molecular oxygen. The team suddenly discovered abundant molecular oxygen in the comet's atmosphere. Being highly unstable, usually oxygen pairs with hydrogen to create water. It might also pair with carbon to create carbon dioxide.

O2 has been discovered twice earlier in space in star-forming nebulas, according to Phys.org. Comet 67P/Churyumov-Gerasimenko may have got oxygen expelled once it became frozen in the comet since the solar system was born 4.6 billion years ago. But why didn't the oxygen react with other chemicals during that period?

Konstantinos P. Giapis, who was a Caltech Professor of chemical engineering, began to explore the Rosetta data related to oxygen due to the chemical reactions on the surface of the comet. He agreed that the reactions were just like the ones that he has been undertaking in the lab for the past two decades. The team looked at the chemical reactions that involved high-speed charged atoms, or ions colliding with semiconductor surfaces and created speedier computer chips and bigger digital memories.

In a new Nature Communications study, Giapis as well as his co-author, postdoctoral scholar Yunxi Yao, show in the lab that the comet is producing oxygen. Even as the comet is heated up by the sun, the water vapor molecules are seen to be streaming off the comet. Ultraviolet light ionizes or charges the water molecules. The sun's wind then blows the ionized water molecules back to the comet. Once the water molecules hit the comet's surface, the oxygen in rust and sand materials are able to take up other oxygen atoms from the surfaces. They enable the formation of molecular O2.

"We had no idea when we built our laboratory setups that they would end up applying to the astrophysics of comets," says Giapis. "This original chemistry mechanism is based on the seldom-considered class of Eley-Rideal reactions, which occur when fast-moving molecules, water, in this case, collide with surfaces and extract atoms residing there, forming new molecules."

He said that all the required conditions for similar reactions are present on comet 67P. The molecular oxygen that was discovered by Rosetta was not "primordial" but was probably produced on the comet's surface in real time.